1. Field of the Invention
The present invention relates to novel polynucleotides encoding proteins involved in biosynthesis of amino acids including phenylalanine, tryptophan, tyrosine, aspartate, lysine, methionine, or threonine, derived from microorganisms belonging to methylotrophic bacteria and fragments thereof, polypeptides encoded by the polynucleotides and fragments thereof, polynucleotide arrays comprising the polynucleotides and fragments thereof.
2. Discussion of the Background
Amino acids such as L-lysine, L-glutamic acid, L-threonine, L-leucine, L-isoleucine, L-valine and L-phenylalanine are industrially produced by fermentation by using microorganisms that belong to the genus Brevibacterium, Corynebacterium, Bacillus, Escherichia, Streptomyces, Pseudomonas, Arthrobacter, Serratia, Penicillium, Candida or the like. In order to improve the productivity of amino acids, strains of the aforementioned microorganisms that have been isolated from nature or artificial mutants thereof have been used. Various techniques have also been disclosed for enhancing activities of L-amino acid biosynthetic enzymes by using recombinant DNA techniques to increase the L-amino acid-producing ability.
L-amino acid production has been increased considerably by breeding of microorganisms such as those mentioned above and by improvements in production methods. However, in order to meet a future increase in the demand for L-amino acids, development of methods for more efficiently producing L-amino acids at lower cost are still desired.
Conventional methods for producing amino acids by fermentation using methanol, which is a raw fermentation material available in large quantities at a low cost, employ Achromobacter or Pseudomonas microorganisms (Japanese Patent Publication (Kokoku) No. 45-25273/1970), Protaminobacter microorganisms (Japanese Patent Application Laid-open (Kokai) No. 49-125590/1974), Protaminobacter or Methanomonas microorganisms (Japanese Patent Application Laid-open (Kokai) No. 50-25790/1975), Microcyclus microorganisms(Japanese Patent Application Laid-open (Kokai) No. 52-18886/1977), Methylobacillus microorganisms(Japanese Patent Application Laid-open (Kokai) No. 491793/1992), Bacillus microorganisms(Japanese Patent Application Laid-open (Kokai) No. 3-505284/1991) and others.
However, only a few methods have been described for producing L-amino acids using Methylophilus bacteria in conjunction with recombinant DNA technology. Although methods described in EP 0 035 831 A, EP 0 037 273 A and EP 0 066 994 A have been described as methods for transforming Methylophilus bacteria using recombinant DNA, applying recombinant DNA techniques to improvement of amino acid productivity of Methylophilus bacteria has not been described. Only WO-00/61723 and WO-02/38777 disclose the improved production of lysine and phenylalanine, respectively, using genes involved in biosynthesis of each respective amino acid. In particular, WO-00/61723 discloses the ask gene, the dapA gene, the dapB gene, and the lysA gene, which encode aspartkinase, dihydrodipicolinate synthase, dihydrodipicolinate reductase, and diaminopimelinate decarboxylase, respectively. WO-02/38777 discloses the aroG gene and the pheA gene, which encode 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase and bi-functional enzyme of chorismate mutase and prephenate dehydratase, respectively.
Therefore, prior to the present invention, only the ask gene, the dapA gene, the dapB gene, the lysA gene, the aroG gene and the pheA gene have been disclosed. Other genes isolated from Methylophilus bacteria that are involved in amino acid biosynthesis and which can be used to improve the yield of amino acids in cultured microorganisms remain elusive and undisclosed.